Many types of input devices are available for performing operations in a computing system, such as buttons or keys, mice, trackballs, touch sensor panels, joysticks, touch pads, touch screens, and the like. Touch screens, in particular, are becoming increasingly popular because of their ease and versatility of operation as well as their declining price. Touch screens can include a touch sensor panel, which can be a clear panel with a touch sensitive surface, and a display device such as a liquid crystal display (LCD) that can be positioned behind the panel so that the touch sensitive surface can substantially cover the viewable area of the display device, and can include displays that have touch sensing circuitry integrated into the display, for example, integrated into the display pixel stackup, which is the stackup of material layers that form the display pixels. Touch screens generally can allow a user to perform various functions by touching or near touching the touch sensor panel using one or more fingers, a stylus or other object at a location dictated by a user interface (UI) including, for example, virtual buttons, keys, bars, displays, and other elements, being displayed by the display device. In general, touch screens can recognize a touch and the position of the touch on the touch screen, and the computing system can then interpret the touch in accordance with the display appearing at the time of the touch, and thereafter can perform one or more actions based on the touch.
In the case of some touch screens, a physical touch on the display is not needed to detect a touch. For example, in some capacitive-type touch screens, fringing fields used to detect touch can extend beyond the surface of the display, and objects approaching near the surface may be detected near the surface without actually touching the surface. Capacitive touch sensor panels can be formed from a matrix of drive and sense lines of a substantially transparent conductive material, such as Indium Tin Oxide (ITO), often arranged in rows and columns in horizontal and vertical directions on a substantially transparent substrate.
Because display and touch capabilities can impose different requirements on the touch screen, it can be challenging to mesh those requirements so that the touch screen can perform both display and touch capabilities effectively and efficiently. In particular, as the circuitry of touch sensing systems of touch screens becomes more integrated with (e.g., are disposed closer to or shared with) other circuitry of the touch screen, such as the circuitry of the display system, the other circuitry may interfere with touch sensing operation due to, for example, crosstalk, stray capacitances, etc.